The present application claims the benefit of priority to SE-9900280, filed Jan. 28, 1999.
The present invention relates to a relay or contactor, wherein measures are taken to facilitate assembly and disassembly in installation and maintenance. By way of construction, the inventive contactor also contributes to better security in operation and service. More specifically, the invention suggests a contactor that is structured to permit assembly and disassembly only in a specified sequential operation.
Typical contactors of this kind have an electric magnet for non-manual operation of contacts to close and break, respectively, an electric current circuit, e.g. a triple-pole alternating current. Control current is supplied to a coil of the electric magnet, and a magnet movement is employed for closing or breaking the electric circuit. In addition to main contacts, the contactor also has secondary contacts and current connections for the control current, that may be controlled manually or electronically.
Contactors of this kind are employed in industrial applications as motor switches, e.g., and are commonly installed at supply central units to which system current and control current is supplied to feed multiple current consumers. Thus, the central units may receive a large number of electric conductors, so that major caution is required in service operations for maintenance, repairs or for replacing worn out components. Such service may expose technicians and other personnel to a latent risk of injury. Usually, switches for the control power are situated away from the central unit, so that service personnel may not at all times be in complete control of the status of the electric magnet. This situation involves the risk of the system power being unintentionally supplied during service, e.g. when replacing the main contacts of the contactor.
In service operations on such installations, it is therefore a desire and a problem to facilitate the work on the contactor, and concurrently to minimize the risk of engagement with electrified circuits.
It is further desirous to reduce the length of service interrupts for maintenance work, by facilitating access to worn out components in replacement works. It is also desirous to minimize the number of separate details needed for assembly and disassembly of the equipment in connection with service operations.
The object of this invention is to meet the above-identified desires, and to solve the problems arising therefrom.
According to the invention, these objects are met in a contactor comprising a contactor enclosure that is sequentially detachable in two successive steps, each step depending from the other. In a first step, the components of the control power circuit as well as the contacts for the system power circuit are unitarily detached in order to permit access to the system power contacts. In said first step, the contacts of the control power circuit are still enclosed by a detachable part of the contactor enclosure. Then, in a second step, access is made to the components of the control power circuit by opening the detachable part of the enclosure. A main feature of the invention is that the two steps for opening the enclosure are both controlled by a number of common locking elements, formed to engage alternative arresting seats for partial or complete access to internal components and operative details of the contactor, thereby avoiding an unintentional supply of system power when the contactor enclosure is detached in said first step.
The characterizing features of the invention are defined by independent claim 1, and preferred embodiments are defined in the sub-claims.